Two-way signaling system



0ct. ll, 1932.

Filed Dec. 4. 199

" ceiving circuit.

Patented Oct. 11, 1932 UNITED STATES ROBERT civiarHEs, 0E WYOMING, NEW JERSEY, Assieivoa To BELL TELEPHONE :LAB-

niez-@ii Aerica I ORATORIES, INCORPORATED, OF NEW YORK, N. Y., .A COVRPORATON-VOF NEW YORK TWO-WAY l sieimriiive sYs'rEivi Applicationled Deceinberll, 1929. Serial No. 411,423.' i

This invention relates to the transmission of signal Waves, and its object is to produceV telephone subscribers circuits with a long' two-Way telephone cable of high attenuation, e. g. a deep sea submarine telephone cable. The high attenuation of the two-Way cable in such a system necessitates the use of amplifying means for the signaling currents at the cable terminals. In such a system also, signal-controlled circuit-control apparatus 4is commonly used in connection With the oppositely directed amplifying paths at the cable terminals to insure that the systeni is operative to transmit in only one direction at a time, so as to s-uppress effectively echoes or singing, or both. This is usually accomplished by making the circuit-control apparatus responsive to transmission of signaling energy over the system in one direct-ion to render the system operative in that direction, and to effectively disable the systein for transmission in the opposite direction.

In such a system as has been described the transmitting and receiving amplifiers in the one-Way transmitting and receiving lpaths respectively at each terminal of the cable are usually associated with one end of the cable through coupling means such as a hybrid coil or a `Y-connect-ion. Because of the inseparable-connection of the transmitting and receiving amplifiers, a considerable amount of energy from the transmitting amplifier in the transmitting circuit at each terminal may be transferred through the coupling means to the receiving amplifier in the re- In spite of the best cable balance, some noise from the output of the transmitting amplifier, when it is not transmitting, Will get into the receiving branch and interfere With reception therein.V Also during` transmission, the receiving amplifier may be badly overloadedY by imbalance energy transmitted through the coupling means from the transmitting amplifier.

In accordance with the-present invention l this interference With reception o r the over-l loading of the receiving amplifiers in such a system is prevented by arranging thecir-v cuits at each terminal of the cable 'so that i duringlreception', the transmitting branch will be disabled in the output ofthe transmitting' amplifier therein, While thereceiving branch is normally operative, or is made operative by the incoming signalingenergy, and during transmission, in response to the transmitted energy the 'transmitting branch will be made operative, and the re-1 ceiving branch will be disabled in the' inputl of the receiving amplifier. i

For convenience the invention will be described as applied to a system for the, two- Way transmission ofspeech Waves, but itis apparent that they principles thereof'applyequally vvell to systems for the transmission of signal Waves in general comprising ,frequencies Within or outside thelspeech frequency range, such as-Waves representing speech, entertainment programs comprising music as- Well as speech, etc. Also the fre-` quency band need not be continuous, but may c `consist of superposed -narrovvT bands, as in the case of multiplex carrier transmission.

In the following description of the invention reference Will be made to the accompaii'yf ing drawing, the single figure of Which shows a schematic circuit diagram of `a cableterminal embodying the invention. y

The terminal station of the drawing-isv shown as connecting a tivo-Way line TL, such as a land telephone line, to the West end of a tivo-Way cable TC of highatteiiuation,

such as a deep sea submarine telephone cable. i This West terminal station comprises a transf mitting circuit TA for repeating Waves from f the line TL into the cable vTC, and av receiv? ing circuit RA for repeating Waves received from the cable TC into the line TL.

The output of the transmitting circuit-TA and the input of the receiving circuit RA are shown connected directly to each otherand to the cable by an ordinary Y-conii`ection,`

but may be connected to each other and the cable by means of a hybrid coil bridge circuit or any other typeot coupling means. The

Vinput oi the transmitting circuit TA and the output of the receiving circuit RA are shown connected to each other and to the line TL by means oli a three-winding transformer or hybrid coil H1A and a balancing network i N1, but may be connected to each other and the line'in any other suitable manner. p

Connected-in Vthe transmitting circuit TA l between the hybrid coil H1 and the cable TC prising the signal-controlled, relay controll- Y so ing deviceS, and the windings of relays 9, 10 and 11 connected in parallel to the output of the devicel 8.. Similarly, connected to the receiving circuit RA between the output 0i amplifier 4 and the input of delay circuit 5 is' a control path 12 comprising a signal-controlled,` relay controlling device 13, and the winding of a relay 14 connected to the output of device 18.

In the transmitting circuit TA- between the output of amplifier' 3 and the cable TU is a'normally open switch 15 adapted to be closed by the o eration of relay 9. Inthe receiving circuit A between the cable TG and the input of amplifier i is a normally closed switch 16 adapted to be opened by operation of relay 10. In transmitting circuit TA between the point of connection of the control circuit 7 thereto and the output of amplifier 1 is a normally closed switch 17 adaptedv to be opened by operation of Vrelay 14;. In the receiving circuit-RA between theoutput of delay circuit 5 and the V input of amplifier 6 is a normally closed' switch 18 adapted to be opened by operation of relay 11.

p It is seen that the west cable terminal circuit which has just been described is of the form which is lrnown in the art as semi-biased, i. e., the circuit is normally; operative t0 transmitl waves between the line TL and the cable TC in one direction, and transmission in the opposite direction depends on a Y switching operation.

. The one-way ampliiiers 1, 3, 4- and 6 may be any ofthe types well known in the art. The amplifier 1 is adjusted so as to amplify the incoming signal waves received from the line TL at least to a level suiiicient to cause operation of the signal controlled, relay controlling device 8 to operate relays 9, 10 and 11. The amplifier 4 is adjusted so as to amplify the received signal waves from the cable Vfor a similarv purpose in TC to a level suiiicient to cause operation oi'l the signal-controlled, relay controllinv` device 18 to operate relay 14. Amplilier 3 is adjusted so as to amplify the signal wavesr in the output of delay device 2 to a level suiiicient to compensate, at least in part, for the attenuation which will be produced. in transwhich will respond to electrical waves i111-, ypressed on their input circuit to control the operation ci' a relay r relays connected to their output circuits. n

The delay circuits 2 and 5 typey wheawill produce avr delay of a required amount, which will be lspecilied below, in electrical 'waves in transmission therethrough, as, for. example, a low Apass lilter, such as disclosed in the United States patents to Campbell,-1,22Z ,113 and 1,2%?,11/1-, issued May 22, 191'?, ora network such disclosed. .Arnold Patent er 15, 1925.

1,565,302, issuedlecen Since the terminal stationsr at both ends of may be of Vany the cable TC may be substantially identica-l ink construction, except perhaps for the amplilication factor ci the amplifiers used, which will depend upon tlie'characteristics orn thecircuits associated Vwith the cable terminal, it has been deemedsuihcient to illustrate only the terminal station at one end of the cable,

- the west end, and in the following description the method of operation oi the system will be clear from reference to Vthe lsingle station shown. Also, as the system operates in similarmanner when the direction of Vthe signal waves is from west to east when it is from east to west, the operation of the system in the former case need vonly be described.

`When no currents are being received over the cable TC in the direction from east to west, or when the currentsV received [thereover when amplified by ampliiier Ll are stiilcf insuiiicient level to cause the operation ci' control device 18 tov energize the winning of relay 14, the switch 17 in the circuit TA is in the closed condition illustrated in thedrawing. Similarly, when no currents are being received over the line TL in the direction from west to east, or the currents being received therecver when amplified by amplilier 1k are still or" insuiicient levelto cause the operation of control device Sto encrgizethe windings of relays 9,10 11, switches 18 and 16 are in the closed condition and switch the line TL. These waves will be impressed by hybrid coilH1 on the transmittingv circuit TA, transmitted thereover to amplifier 1 and amplified thereby. The amplified waves in the output of amplifier' 1 `will be divided between the input of dela'ycircuit 2 and the input of control path 7. Themain portion of the amplified waves in the output of amplifier 1 will 'be transmitted through delay circuit 2, being delayed intransmission' therethrough for a certain period.

The transmitted waveswill then be amplified by amplifier 3.

`A small portionof the amplified waves in the output of amplifier 1 will be diverted into thecontrolpath 7,- and will operate the control device 8 therein causing the windings of relays 9, and 11- to be energized. Relay 9 will operate to close the normally open switch 15 in the outputy of transmitting circuit TA to make that circuit operative to transmit from the output of amplifier 3 to the cable TC. Relays 10 and 11V are adjusted to operate sub-l stantially simultaneously with orbefore relay 9 to vrespectively open the normally closed switches 16 and 18 in receiving circuit RA.

The opening of switch 1G will prevent any transmi-ssion of waves from the cable TC, or from the output of the transmitting circuit TA to the input of amplifier 4, and thuswill prevent overloading of that amplifier.

Delay circuit 2 in the transmitting circuit TA is-designed to produce sufficient delay in the speechfwaves transmitted therethrough to prevent their arrival at switch in the output of amplifier 3 until after thatswitch has been closed by the-operation of relay 9. The speech waves after amplification by amplifier 3-will therefore be transmitted from the output of amplifier 3 directlyto the cable TC and will be transmitted thereover'to the east terminal station. Y

.Relay'Q is designedso as to remain operated for a definite period of time after the input of speech energy to the control path 7 ceases, so as tok prevent clipping of the speech, i. e., loss of the portion of the speech which hasnot reached the switching point in transmitting circuit TA (switch 15) at the: time the control `device 8 releases due to a fall in the level ofthe waves impressed onits input. Similarly, rela-y 10is designed so that .it will remain operated for a definite period of time after the control device 8 has released so as to insure that the switch 16 in path RA will remain open at least until all-ofl the speech energy passing over the transmitting circuit TA has been sent int-o the cable TC. This will prevent false operl' ation of the control device 13 inicontrol path` 12 connected to the receiving circuit RA. Relays 9 and 10 may be so designed by .well known mechanical construction making them slow to release, or by the use .of an electrical auxiliary hangover circuit in connection with the relays, such as disclosed,for example,I in the copending application of J. Herman, l

Serial No. 144,848, filed October 28, 1926.V

The operation of the circuits at the terminalstation at the east end ofthe cable TC in response to the speech waves transmitted thereto will be made clear by describing the operationof the similar circuits at the westterminal station shown in the drawing, in response to waves received over the cable TC. The speech waves incoming over `cable TC will be transmitted directly into the inputof the receiving Vpath RA at the west terminal, as the output of the transmitting circuit VTA is disabled because Vof the normally open switch 15 therein. The normally openswitch 15 in the output of transmitting circuit TA also pre-vents theV transmission of any amplified energy which may be present in the output of amplifier J Vo when speech waves are Anot being transmitted over the circuit TA, such as amplified noise, from the outputof transmitting circuit TA to the input of receiving circuit RA through the icouplingtherebetween.' T,

this amplified noise were transmitted into receiving'circuit RA, it might, of course, seriously interfere with reception in that cir'- cuit.

TC will be amplified by amplifier 4 in receiving circuit RA. The amplified waves in the output of the amplifier 4 will be divided, the main portion being transmitted to the inputvofzdelay circuit 5and agsmaller portion being diverted into control path 12.

VThe portion of the speech waveszdiverted into control path 12 will operate control de-V vice 13 therein causing the winding of relay 14: in the output thereof to be energized. Relay 14 will ope-rate toopen the normally closed switchrl'k in the input of the transmitting circuitTA. The circuit TAv will,

therefore, be rendered inoperative to tra-nsmit waves from the line TL, or unbalance energy from the output of the receiving cir-'i cuit` RAzp-assing through the coupling. H1, thus preventing false Aoperation of relays 9,

10 and 11. The vmain portion of the speech waves in the output of amplifier 4 in re speechY waves therethronghfor an'sufcient.Y

The incomingspeech waves from the cable` time interval to insure that switch 17 in the input of transmitting circuit TA is Closed by relay'la in suffucienttime to prevent any unbalanced signaling energy from hybrid coil H1 getting into the control circuit .7 to cause false operation of relays 9, 10 'and 11.

The relay 14 may be designed to remain operated for the required length of time after the cessation of supply of speech energy to the input of control circuit 12 to prevent the closing oi the switch 17 in the receiving circuit RA until after all of the east to west speech waves have, been transmitted into'the circuitV TL from the output of the'receiving circuit RA. rThe premature closing of switchv 17 might resuliJ in `false operation of the relays 9, and 11 by unbalanced energy transmitted through the hybrid coil H1. The relayV 14- may be maintained operated for the required length ottime by making it slow Yto release byv well known methods of mechanical design, as indicated in the drawing or by associating with this relay an auX- iliary hangover circuitl such as disclosed in the copending application of J. Herman reterred to above.

Although in theiembodiment of the invention which has beenillustrated and described,

I electromagnetic relays-are employed for con ditioning the ampliiier` paths by operating movable switches to Vclose or open-circuit these paths, thelinvention isy not limited to such conditioning means. is within the scope of the invention to disable 'the transmission paths by short-circuits or loss circuits, instead of open circuits, inserted in the paths controlled by current controlled relays; Stationary devices having no `movable elements may be employed in place l, of themechanical relays shown in the drawj amplifier and normally operative in the input of the receiving ampliiier, it is 'within' the scope of the invention yto have both the output of the transmitting amplifier'and the input orP the receiving ampliiier normally disabled, in which case the control path asso'- ciated with the transmitting circuit need only be responsive to currents to be transmitted to render the transmitting circuit operative to transmit from the line TL to the cable TC, and an additional control path may be connected to the input ofthe receiving circuit and made responsive to signal waves received over the cable TC to render the receiving circuit operative between the cable JTC and the receiving amplifier. Although For example, it

in the terminal circuit illustrated and described, botli the input of the transmitting circuit TA and the output of the receiving.

-circuit have been shown as normally opera'v tive, itis within the scope of theV invention to have either one-or both of these' circuits normally disabled in which ease the control paths associated with these paths may beA ar- 7 ranged to make the disabled circuit Aoperative in response Vto currents to be transmitted thereover to the cable TG or to the circuit TL.

v Although in vthe terminal circuit. which has beenl illustrated .and described, the re-l ceiving circuit and they transmitting circuit have been shown normally disabled or adapt ed to be disabledy in Jtwo places, because of the highL gain of the apparatus necessary in' terminal circuits of this type, itmay be desirable to have the transmitting and receiving circuits normally disabled,or adapted to be disabled in more than two places by means similar to those shown'. f

Certain deviations from the system which may be made within the scope of the invention have been mentioned above. Other alternatives or modiiications will readily occur to one skilled in the art in connection with adapting the invention to 'diilerent transmission requirements. The invention is not toy be construed, therefore, as limited to the specilic disclosure, but its scope is defined in the appended claims.

What is claimed is: f

1. A terminal circuit for a two-way transmission line, saidcircuit comprising a source of waves to betransmitted over said'line, a transmitting circuit and a receiving circuit eachy including amplifying means, vcoupling means connecting said transmitting circuitr and vsaid receiving circuit to said line, means normally disabling said transmitting circuit for transmitting waves from the output Yof the amplifying Ymeans therein to said Vcou-A pling means, meansY under control of the waves received from said source for rendering said transmitting circuit operative to transmit said received waves to said line, and i for substantially simultaneously disabling` said receiving circuit `ior transmitting waves between said coupling means and the ampli- Y .tying means in said receiving circuit, and

means under control of the waves received by said receiving circuit froml said line for ef-V iectively disabling said transmitting circuit in the input oi the amplifying means therein.

2. A two-way .transmission system comprising a, section of two-way line, two oppof sitely directed' one-way line sections each including amplifying means, means connecting the output of one and the input of the other or' said one-way line sections to one end of said two-way vsection of line, means normally disabling said one one-way section of linev in the output of the amplifying means therein, means responsive to transmission in said one:

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one-way section of line for rendering said one one-way section operative to transmit to said two-way line section, and for disabling said other one-way section in the input of the amplifying means therein, and means responsive to transmission from said two-way line section to said other one-way line section for disabling said one one-way line section in the input of the amplifying means therein.

3. A two-way transmission system lcomprising two two-way line sections, two oppoeV sitely directed one-way transmission circuits each including amplifying means, means cou@ pling the input of one and the output of the other of said one-way circuits to one of said two-way line sections and the output of said one and the input of said other one-way circuit to the other of said two-way line sections, means normally disabling said one transmission circuit in the output of the amplifylng means therein, means responslve to transmission from said one two-way line section to said one one-way transmission circuit to disable said other one-way line section in the input and in the output of the amplifying means therein, and to render operative said one one-way line section for transmission to said other two-way line section, and means responsive to transmission from said other two-` way line section to said other one-way circuit for disabling said one one-way circuit in the input of the amplifying means therein.

4. The system of claim 3 and in which said one one-way transmission circuit includes transmission delay means connected between the normally disabling means therein and said means responsive to transmission from said one two-way line section, and in which said other one-way transmission circuit includes transmission delay means connected between the disabling point in the output of the amplifying means therein and said means responsive to transmission from said other two-way line section.

5. A two-way transmission system comprising two two-way line sections, two oppositel-y directed one-way transmission circuits,

each including amplifying means, means coupling the input of one and the output of the other of said one-way circuits to one of said two-way line sections, means coupling. the input of said other one-way circuit and the output of said one one-way circuit to the other of said two-way line sections, and means responsive to transmission from said one two-way line section to said one one-way circuit for effectively disabling the input and output of said other one-way circuit.

6. A two-way transmission system comprising two two-way line sections, two oppositely directed one-way transmission pathsV each including amplifying, means, means coupling the input of one and the output of the other one-way path to one of said two-Way line sections, means coupling the input of said other and the output of said one one-way path tothe other of said two-way line sections, control means connected to said one one-way path and responsive to transmission therein to disable said other one-way path,

control means connected to said other one 

